As summarized by Science Magazine, life on Earth subsists in one of two ways: conversion of light via photosynthesis into an energy form which can be stored as a hydrocarbon, which can then be used later via oxidation, OR by simple theft – i.e., eating other organisms and stealing their stored energy in the process.
Now we have a report of a third way – using radiation:
Source: NASA
[Desulforudis audaxviator] takes a third path: It draws its energy from the radioactivity of uranium in the rock in the mine. The radiation from decaying uranium nuclei breaks apart sulfur and water molecules in the stone, producing molecular fragments such as sulfate and hydrogen peroxide that are excited with internal energy. The microbe then takes in these molecules, siphons off their energy, and spits them back out. Most of the energy produced from this process powers the bacterium’s reproduction and internal processes, but a portion of it also goes to repairing damage from the radiation.
I think it’s important to note that this is not a direct interaction with radiation, but rather taking advantage of a result of radiation – in a sense, the molecular fragments, fraught with internal energy, are the primary actors, and the process which produces them – radiation – is primarily important only in that it produces these fragments, although there is a secondary importance in that it can damage Desulforudis audaxviator in the process.
The Science article goes on to note that cosmic rays could take the place of uranium-based radiation on the surface of a planet dissimilar to Earth, thus giving organisms on those planets a shot at life, and this is exciting for exobiologists. I think it also gives exobiologists another way to consider how life might find ways to survive – thus leading to new tests as we explore Mars, Europa, and other potential harbors of life.
